U.S. Pat. No. 4,477,176 granted Oct. 16, 1984 to M. J. Russel shows a color reproduction apparatus utilizing an electrophotosensitive web which is driven through an endless path. The web is uniformly charged and exposed to a series of color separation light images of an original to create latent electrostatic images. The images are developed with toners of different color to create visible color images and are transferred in registry to a receiving surface to form a multicolor image. The images are exposed by flash. Similar to monocolor apparatus using flash exposure, the flash is triggered by physical or optical sensing of a perforation (herein sometimes called "perf") associated with the image area to be exposed.
The quality of the multicolor image formed at the transfer station is dependent on several factors, one of which is the accuracy of the timing of the flash exposure. More specifically, if one exposure is early or late compared to the others by even an extremely small amount, this will show up in a slight difference in the location of the two images on the resulting multicolor reproduction. This misregistration shows up as both a loss of image sharpness and a change in hue of colors intended to be formed by combining toners. The structure shown in the Russel patent gives good results in most applications. However, accuracy in forming perforations in webs when such webs are manufactured in quantity is not adequate for the highest quality color production. Put another way, perforations formed in the edges of webs within tolerances acceptable for the highest quality camera and projector work can still be off enough to be noticeable when trying to do high quality color reproductions on this prior apparatus.